CAAC‐Based Thiele and Schlenk Hydrocarbons

• Published in: Angewandte Chemie Vol. 132; no. 17; pp. 6795 - 6800
• Main Authors: Maiti, Avijit, Stubbe, Jessica, Neuman, Nicolás I., Kalita, Pankaj, Duari, Prakash, Schulzke, Carola, Chandrasekhar, Vadapalli, Sarkar, Biprajit, Jana, Anukul
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 20-04-2020
• Subjects: Analogs; Carbene; Chemistry; Dimerisierung; Dimerization; Dimers; Hydrocarbons; Konjugation; Organic compounds; Radikale; Strukturaufklärung
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201915802

Diradicals have been of tremendous interest for over a century ever since the first reports of p‐ and m‐phenylene‐bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non‐Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head‐to‐tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox‐active organic compounds.
Doppelt radikalisch: Die p‐ und m‐Phenylen‐verbrückten Bispyrrolinium‐Kationen A bieten Zugang zu den cyclischen (Alkyl)(amino)carben(CAAC)‐Analoga des Thiele‐Kohlenwasserstoffs B, einem Kekulé‐Diradikal, bzw. des Schlenk‐Kohlenwasserstoffs C, einem Nicht‐Kekulé‐Diradikal. B hat einen Singulett‐Grundzustand. C hat zwei ungepaarte Elektronen im Grundzustand und bildet durch eine intermolekulare doppelte Kopf‐Schwanz‐Dimerisierung ein Dimer.